American Academy of Environmental Engineers

Background

In 1999 the Town of Glastonbury acquired the Field Holstein Property, a former bulk petroleum storage facility containing 15 above-ground oil storage tanks. An ‘eyesore’ with extensive soil and groundwater contamination by Light Non-Aqueous Phase Liquids (LNAPL). this “Brownfield” site also bordered the scenic Connecticut River, making it a potentially valuable public asset if it could be remediated to stringent state standards.

After preliminary investigations, Malcolm Pirnie designed a demolition plan to remove and recycle the tanks, then developed a Remedial Action Plan (RAP) — an innovative remediation approach providing a roadmap for compliance with state cleanup standards.

Time and budget issues threatened achieving the multiple objectives of remediation and redevelopment for public access and recreational uses, including a new Community Center:

A tight Town budget limited by public referendum.
An extremely accelerated remediation schedule driven by Community Center construction.
Need for both soil and groundwater cleanup to attain a CTDEP “Covenant Not to Sue,” critical for minimizing future Town liability and demonstrating site safety.

Conventional options wouldn’t meet Town goals:

Excavation and off-site disposal of <30,000 cubic yards of contaminated soils would require excavation well below the groundwater table — prohibitive due to disposal costs, permitting requirements and constructability issues.
On-site bioremediation of soil and groundwater wouldn’t achieve the Center construction schedule.
A pump and treat system groundwater remediation system would have meant long-term cost and operational burdens.

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Innovative Approaches Integrate Multiple Objectives

Malcolm Pirnie devised a creative, integrated approach to handle all affected environmental media:

on-site relocation of contaminated soils exceeding Direct Exposure Criteria (RDEC)
removing only soils exceeding the Pollutant Mobility Criteria (PMC)
<>mitigating LNAPL seeps to the River adjacent to the site.

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Managing Contaminated Soils. CTDEP regulations specify a 4-foot cover of clean soil for on-site disposal of materials exceeding RDEC to prevent possible human exposure. Malcolm Pirnie’s innovative grading plan covered or relocated soils away from future construction; grading complemented future site use, protected the public and minimized disturbance of sensitive wetlands.

To provide enough space onsite to relocate all RDEC soils while avoiding creating new contaminated footprints, Pirnie’s plan specified mounding 4 feet of clean fill above these soils; this created a centrally located amphitheatre structure that both met regulations and provided a physical feature adaptable for future park use. Off-site disposal requirements were cut nearly in half —saving about $625,000.

Managing Contaminated Groundwater. To mitigate contaminated groundwater, Malcolm Pirnie implemented a passive “funnel and gate” system, an 850-foot-long barrier wall that creates a three-dimensional barrier to groundwater flow. By directing impacted groundwater to specific locations for oil collection without pumping, this eliminated conventional “treatment” system monitoring and O&M costs and minimized construction complexity. State-of-the-art groundwater modeling confirmed no adverse on-site effects such as raising groundwater table elevations or significantly changing normal groundwater flow, and also determined optimum oil skimming locations.

When some 2,500 cubic yards of buried asphaltic sludges were unexpectedly found that were not viable for landfill disposal or remaining on-site, based on traditional mass-based analysis, Pirnie worked with CTDEP, using alternative chemical analysis (synthetic precipitation leaching procedure methods) to demonstrate that the materials could be safely relocated on-site. This eliminated possible off-site disposal costs of $300,000.

Social/Economic Considerations

The potential social and economic benefits reflect the Town’s vision for the property. An environmentally contaminated site has become an invaluable community asset. A Riverfront Park will give residents access to the River for recreational activities, and the Community Center will provide a place for large community gatherings, both indoor and outside – resulting in additional investment in the Town and its residents.

A further benefit relates to the significant development pressure on the Town’s remaining open space. By electing to remediate a Brownfield site for the Community Center, the Town not only cleaned up a contaminated property, but also preserved a large amount of its open space.

One of this project’s most significant issues was public perception. Seen by Glastonbury residents as an eyesore, changing public perception was key when it was proposed as a Community Center and Riverfront Park site. The public not only had to consider it not a liability, but also recognize it was safe for recreational activities -- this meant remediation had to earn the CTDEP Covenant Not to Sue. With this successful project, public perception changed from an eyesore to a safe venue for the community.

Complexity

The very sandy soils and location of barrier close to the stream channel encroachment line made conventional open-cut construction techniques too difficult and costly to implement. Installing HDPE sheeting as a barrier wall, easily driven through the sandy soils, was a cheaper alternative to conventional steel sheeting or slurry walls. Constructed along the length of the observed LNAPL seeps, and keyed into the existing clay layer, the wall provides a three-dimensional barrier preventing groundwater and LNAPL flow from directly reaching the Connecticut River. The three gates, or sumps, equipped with oil-skimming pumps, provide oil collection points while allowing groundwater to pass through towards the River. Collected LNAPL is then pumped to on-site underground storage tanks.

A small volume of soil exceeded the Direct Exposure Criteria for Polychlorinated Biphenyls (PCBs), precluding them from onsite disposal. Complex EPA guidelines required a thorough characterization of PCB-contaminated soils by sampling before removal and confirmatory sampling following excavation and off-site disposal. Completing these activities within already tight time constraints, without hampering other remediation activities, was a significant challenge.

Quality/User Satisfaction

Remediation activities were completed in March 2004, eliminating sources of continued groundwater contamination, and mitigating the release of LNAPL into the Connecticut River. The project has created a more enjoyable waterfront environment, the new Community Center is under construction on schedule, and the Town now has a site available for public use. It minimized future risks and liabilities and met a referendum-based budget and strict environmental regulatory standards.

By using creative approaches, Malcolm Pirnie turned an eyesore and an environmental liability into a valuable community asset, with no stigma of past pollution that would limit public use.

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